Xuan Zhuo
2023-Mar-23 03:45 UTC
[PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
On Thu, 23 Mar 2023 11:38:34 +0800, Yunsheng Lin <linyunsheng at huawei.com> wrote:> On 2023/3/23 9:36, Xuan Zhuo wrote: > > On Wed, 22 Mar 2023 16:22:18 +0800, Yunsheng Lin <linyunsheng at huawei.com> wrote: > >> On 2023/3/22 11:03, Xuan Zhuo wrote: > >>> In the xdp implementation of virtio-net mergeable, it always checks > >>> whether two page is used and a page is selected to release. This is > >>> complicated for the processing of action, and be careful. > >>> > >>> In the entire process, we have such principles: > >>> * If xdp_page is used (PASS, TX, Redirect), then we release the old > >>> page. > >>> * If it is a drop case, we will release two. The old page obtained from > >>> buf is release inside err_xdp, and xdp_page needs be relased by us. > >>> > >>> But in fact, when we allocate a new page, we can release the old page > >>> immediately. Then just one is using, we just need to release the new > >>> page for drop case. On the drop path, err_xdp will release the variable > >>> "page", so we only need to let "page" point to the new xdp_page in > >>> advance. > >>> > >>> Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > >>> --- > >>> drivers/net/virtio_net.c | 15 ++++++--------- > >>> 1 file changed, 6 insertions(+), 9 deletions(-) > >>> > >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > >>> index e2560b6f7980..4d2bf1ce0730 100644 > >>> --- a/drivers/net/virtio_net.c > >>> +++ b/drivers/net/virtio_net.c > >>> @@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > >>> if (!xdp_page) > >>> goto err_xdp; > >>> offset = VIRTIO_XDP_HEADROOM; > >>> + > >>> + put_page(page); > >> > >> the error handling of xdp_linearize_page() does not seems self contained. > >> Does it not seem better? > >> 1. if xdp_linearize_page() succesed, call put_page() for first buffer just > >> as put_page() is call for other buffer > >> 2. or call virtqueue_get_buf() and put_page() for all the buffer of the packet > >> so the error handling is not needed outside the virtqueue_get_buf(). > >> > >> In that case, it seems we can just do below without xdp_page: > >> page = xdp_linearize_page(rq, num_buf, page, ...); > > > > > > This does look better. > > > > In fact, we already have vq reset, we can load XDP based on vq reset. > > In this way, we can run without xdp_linearize_page. > > For compatibility, it is still needed, right?Yes> > > > > > >> > >> > >>> + page = xdp_page; > >>> } else if (unlikely(headroom < virtnet_get_headroom(vi))) { > >>> xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM + > >>> sizeof(struct skb_shared_info)); > >>> @@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > >>> page_address(page) + offset, len); > >>> frame_sz = PAGE_SIZE; > >>> offset = VIRTIO_XDP_HEADROOM; > >>> + > >>> + put_page(page); > >>> + page = xdp_page; > >> > >> It seems we can limit the scope of xdp_page in this "else if" block. > >> > >>> } else { > >>> xdp_page = page; > >>> } > >> > >> It seems the above else block is not needed anymore. > > > > Yes, the follow-up patch has this optimization. > > Isn't refoctor patch supposed to be self-contianed too, instead of > depending on follow-up patch?I mean that the #2 patch do this. Thanks.
Apparently Analagous Threads
- [PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
- [PATCH net-next 2/8] virtio_net: mergeable xdp: introduce mergeable_xdp_prepare
- [PATCH net-next 2/8] virtio_net: mergeable xdp: introduce mergeable_xdp_prepare
- [PATCH net-next 4/5] virtio-net: do not reset during XDP set
- [PATCH net-next 2/2] virtio-net: simplify XDP handling in small buffer